Anisotropic circulator with dielectric posts adjacent the strip line providing discontinuity for minimizing reflections



Jan. 12, 1965 o. L. DRUMHELLER ETAL 3,165,711 ANISOTROPIC CIRCULATOR WITH DIELECTRIC POSTS ADJACENT THE STRIP LINE PROVIDING DISCUNTINUITY FOR MINIMIZING REFLECTIONS Filed June 10, 1960 2 Sheets-Sheet 1 FIG] INVENTOR. RONALD W. KORDOS BY OLIVER L. DRUMHELLER ATTORNEY 1965 o. L. DRUMHELLER ETAL 3,165,711

ANISQTROPIC CIRCULATOR WITH DIELECTRIC POSTS QDJACENT THE STRIP LINE PROVIDING DISCONTINUITY FOR MINIMIZING REFLECTIONS Filed June 10, 1960 2 Sheets-Sheet 2 FIG. 3

IN VEN TOR. RONALD W. KORDOS BY OLIVER L. DRUMHELLER ATTORNEY United States Patent 3,165,711 ANISOTROPIC CHICULATOR WITH DIELEC- TRIU PQS'I'S ADJACENT THE STRIP LENE PRGVIDING DISCQNTINUHTY FOR MINI- MIZING REFLEQIIUNS Oliver L. Drdmheller, Pontiac, and Ronald W. Kordos,

East Detroit, Mich, assignors to The Bendix Corporation, iiouthiieid, hiicin, a corporation of Delaware Filed dune I0, 1960, Ser. No. 35,281 2 Uiaims. ((11. 333-11) This invention pertains to a switching member and more particularly to a Y circulator which is very compact, has good isolation between the arms of the Y, has a low insertion loss and is capable of operatingat a high frequency with a wide band width.

It is an object of this invention to provide between two ground planes a Y circulator having a member such as a strip conductor with a plurality of arms extending from a common center, each arm being connected at its free end with a signal carrying member and with means for causing the signal to pass from one arm to another without entering a third arm, and with further means for providing an electromagnetic wave discontinuity between each of the arms and the ground planes to minimize reflections in the arms to improve circulator characteristics.

Another object of this invention is to provide in such a circulator on either side of the center of the strip condoctor a disc of anisotropic material such as yttrium iron garnet, which concentrates an applied magnetic field in such a manner so as to cause electromagnetic energy flowing along one arm of the member to pass to a second arm and be isolated from a third arm. Tuning wafers are placed between each garnet disc and the respective ground planes with the waters being of a material such as T efion and forming a discontinuity capacitance to further tune the strip transmission line structure.

Another object of this invention is to provide in the aforementioned arms of the strip transmission line structure a reduced portion adjacent the garnet disc for a more uniform impedance along each arm and a reduction in signal reflection.

These and other objects will become more apparent when a preferred embodiment of this invention is considered in connection with the drawings, in which:

FIGURE 1 is a plan view which is partially broken away of a Y circulator of this invention;

FIGURE 2 is a section taken along the lines 22 of FIGURE 1; and

FIGURE 3 is a detailed drawing of the Y-shaped strip conductor used in the circuiator of FIGURES 1 and 2.

In the drawings, a housing 20 has two sections 22, 24, which are bolted together. Portions have been removed along the inner faces of sections 22, 24 to form a center chamber 26, the Walls of which constitute ground planes 27, 27A and in this embodiment are .25" apart. The housing materials may be of aluminum to reduce weight. Formed centrally along the outer surfaces of sections 22, 24 are wells 23, 30, each of which has a pair of fully charged Indox I ceramic magnets 32, 34. Magnets 32, 34 are each 1.079 in diameter and .250" thick. Pole pieces 36, 37, formed of soft iron, are aligned with the magnets 32, 34 and fit into recesses 38, 40 formed respectively in sections 22, 24.

Bolted to housing 20 are three ports 42, 44, 46, which are aligned on axes spaced 120 from one another with each port having a washer 48 of dielectric material fitted in the inner end thereof. A tubular pin 50 is secured in each Washer 43 and has a slot 52 at its inner end and fingers 53 at its outer end for receiving the center conductor of a coaxial cable, not shown.

A strip conductor 56, shown in FIGURE 3, has three Patented Jan. 12, 1965 arms, 58, 60, 62, extending from a common center 64 along axes spaced apart. The ends or" arms 58, 60 and 62 fit into slots 52 of the corresponding tubular members 50 to provide a transition between a coaxial cable end and the strip conductor 56. The length of each arm 58, 60 and 62 in this embodiment is 1" and the width of each arm is .218". The inner or center portion of each arm is reduced in width to .125 for a length of .250" and is then tapered outwardly to the wider dimension along a radial distance of .187" from the outer end of the narrow lengths. This configuration, as will be discussed later, aids in providing uniform impedance along the entire length of each arm to minimize signal reflections in the arms.

Aligned with common center 64 and placed on either side of strip conductor 56 are two discs 66, 68 of anisotropic material which have the ability to concentrate an applied magnetic field from magnets 32 and 34 in such a manner that a signal entering one arm, say arm 58 of the strip conductor 56, will be directed almost entirely to a second arm 60 with little or no signal going to arm 62. By reversing the direction of the magnetic field through members 66, 68, the signal applied to arm 58 will be caused to pass to arm 62 instead of arm 60.

Ferromagnetic materials such as ferrite or garnet are anisotropic in nature and inthis embodiment the material used for discs 66, 68 is yttrium iron garnet available from Motorola, having part No. M-012. This garnet material has a saturation magnetization of 1880 gausses, a line width of 55 oersteds and a Curie temperature of 290 C. For optimum band width, high isolation and low insertion loss characteristics, the size of the discs in this embodiment is .500 in diameter and the height of discs is.

As can be seen from FIGURE 1, the narrow portions of arms 58, 60, 62 coincide with the garnet disc 66. Since the presence of the disc 66 alters the impedance of transmission line structure in the area of the disc, a compensation has been made by narrowing the arms to keep the impedance more uniform and reduce signal reflections which in turn minimizes insertion loss over a broad band of frequencies.

Placed between ground planes 27, 27A of housing 20 and each disc 66, 68, is a thin wafer 70 of dielectric material (FIGURE 2), such as Teflon, for further regulating the impedance of the arms 58, 60 and 62 of strip conductor 56 to provide for more uniform impedance and broader band operation with minimum insertion loss. The Teflon in tuning wafers '70 has a relative dielectric constant of 2.1 and has a loss tangent of .0002. Each wafer 70 is .500 in diameter and is .005" thick.

Placed between each arm 58, 60, 62 and ground planes 27, 27A at a distance of .547" from center 64 are dielectric tuning posts '72 which in this instance are made of Tefion and are .274" in diameter by .096" high. These provide discontinuities which, together with the discontinuities formed by wafers 70, garnet discs 66, 68 and the impedance regulation brought about by the narrowing of the arms 58, 60, 62 near the center of the strip conductor 56, operate together to provide a circulator having a frequency range from 4700 to 5700 megacycles, an isolation of 20 db minimum and 35-40 db peak, an insertion loss of less than 5 of a decibel, and a standing wave ratio of 1.15 mam'mum. In addition, the Y circulator shown is very compact in structure, being only 2.375" in diameter and 1.0" high, while weighing only 11 ounces. The circulator pictured operates satisfactorily over a temperature range of 55 to C. The calculated average power handling capacity is 10 watts and the calculated peak power handling capacity is 10 kilowatts. Also, since there are no moving parts, the device will withstand severe mechanical shock and vibration.

In the operation of the preferred embodiment of this invention, coaxialv cables are connected to ports 44, 46 and 42; A signal applied to port 44 will flow only from arm 58 ofvthe circulator strip conductor 56 to arm 60. Garnets 66, 68 are anisotropic materials and when subject to the magnetic field of magnets 32, 34, distribute RF. electromagnetic fields in such a manner that an electromagnetic wave in arm 58 is almost entirely directed to arm 60. For the same reason a signal-applied to port 46 will flowalmost entirely to arm 62 with little or no signal going to arm 58, and a signal entering arm 62 will flow almost entirely-to arm 58. Of course, this direction can i be .changed and instead of the signal flowing to the arm left of the arm into which itentered, it can be made to flow to the right of the arm into which it entered by merely disconnecting the coaxial cables, turning the circulator over, and reconnecting the cables.

Although this invention has been disclosed and illustrated with reference to particular applications, other applications and modifications'will be apparent to persons skilled. in the art. Such modifications may include tuning the transmission line structure by varying the configuration of the arms at proper places therealong to make them either larger or smaller, resulting in minimum insertion loss for a relatively large band Width. The invention is,

therefore, to be limited only as indicated by the scope of the appended claims.

Having thus described our invention, we claim:

1. A circulator for attachment to a plurality of signal carrying members for directing signals between them in a predetermined manner, comprising a housing having a chamber defined by spaced ground plane means,

I a strip conductor member having at least three arms extending from a center portion outwardly to the ends of the arms, with the center portion being in an inv I a V 4 1 means for producing a magnetic field through said anisotropic means to direct the path of electromagnetic waves along said strip conductor member, means for providing an electromagnetic wave discontinuity to minimize reflections in the strip conductor thereby improving circulator characteristics, said last means comprising localization of material having a-dielectric constant greater than air and positioned along said strip conductor member to create said electromagnetic Wave discontinuities,

' said last means being positioned inwardly of the ends of said arms. 7

2. The circulator of claim 1' with said means for providing an electromagnetic Wave discontinuity comprising localization of dielectric material having a dielectric constant greater than air being between said strip conductor member and said ground plane means, i said localization of dielectric material having a dielectric constant greater than air being positioned along each of said arms intermediately of the circumference of said anisotropic means and the end of each arm.

References Cited by the Examiner UNITED STATES PATENTS 2,920,292 1/60 Scovil et al 333-17 2,958,055 10/60 Rowen 33324.1 1/62 Allin et a1; 333-1.1

. OTHER REFERENCES Electrical Manufacturing, February 1959, pages 61- Harvey: Parallel Plate 7 Transmission, Proc. I.E.E., March 1959, vol. 1063, pages 129-139, TKl 14.

Auld: IRE Transactions on Microwave Theory and Techniques, April 1959, pages 23 8-246.

Yoshida: Proceedings of the IRE, June 1959, page 1150.

Davis et al.: Proceedings of the IRE, January 1960,

pages -116. 

1. A CIRCULATOR FOR ATTACHMENT TO A PLURALITY OF SIGNAL CARRYING MEMBERS FOR DIRECTING SIGNALS BETWEEN THEM IN A PREDETERMINED MANNER, COMPRISING A HOUSING HAVING A CHAMBER DEFINED BY SPACED GROUND PLANE MEANS, A STRIP CONDUCTOR MEMBER HAVING AT LEAST THREE ARMS EXTENDING FROM A CENTER PORTION OUTWARDLY TO THE ENDS OF THE ARMS, WITH THE CENTER PORTION BEING IN AN INWARDLY DIRECTION FROM THE ENDS OF SAID RAMS, SAID ENDS OF EACH OF SAID ARMS BEING ADAPTED FOR CONNECTION TO A SIGNAL CARRYING MEMBER, SAID STRIP CONDUCTOR MEMBER BEING SUPPORTED IN SAID CHAMBER BETWEEN SAID GROUND PLANE MEANS, ANISTOTROPIC MEANS BEING POSITIONED BETWEEN THE CENTER PORTION OF SAID STRIP CONDUCTOR MEMBER AND SAID GROUND PLANE MEANS, MEANS FOR PRODUCING A MAGNETIC FIELD THROUGH SAID ANISOTROPIC MEANS TO DIRECT THE PATH OF ELECTROMAGNETIC WAVES ALONG SAID STRIP CONDUCTOR MEMBER, MEANS FOR PROVIDING AN ELECTROMAGNETIC WAVE DISCONTINUITY TO MINIMIZE REFLECTIONS IN THE STRIP CONDUCTOR THEREBY IMPROVING CIRCULATION CHARACTERISTICS, SAID LAST MEANS COMPRISING LOCALIZATION OF MATERIAL HAVING A DIELECTRIC CONSTANT GREATER THAN AIR AND POSITIONED ALONG SAID STRIP CONDUCTOR MEMBER TO CREATE SAID ELECTROMAGNETIC WAVE DISCONTINUITIES, SAID LAST MEANS BEING POSITIONED INWARDLY TO THE ENDS OF SAID ARMS. 